Aluminum Pressure Plate in a 911SC?

Wrecked944 · 08-05-2002, 07:24 AM

I just happen to have one of those snazzy aluminum pressure plates and my tranny just happens to be out of the car. Sooo...

This is the pressure plate for the 1974-77...Pelican part number P-116-001-16. Is this guy a bolt-in swap for a 1980 9111SC 915 tranny or not? I already have a new TO bearing and TO arm as well and clutch alignment tool. If it doesn't fit, no big deal. Just figured I'd give it a whirl...

Thanks,

Bill Verburg · Bill Verburg's Garage

If its the Sachs 225mm then its perfect, don't forget the pilot bearing while you're in there.

davis911s · davis911s's Garage

I've heard, or read somewhere that the car is harder to idle or something with this install. Anyone ever hear of that, or am I dreaming stuff up again?

I also have one and haven't installed it yet because of that reason.

Shawn

Wrecked944 · 08-05-2002, 07:14 PM

"I've heard, or read somewhere that the car is harder to idle or something with this install. Anyone ever hear of that, or am I dreaming stuff up again?"

I've heard the same thing - though I've heard it is more of a problem with lightweight flywheels than pressure plates. But in theory, either one could contribute to the problem...my understanding is that the weight of the flywheel helps keep the engine spinning when you disengage the clutch and remove the load. Literally the momentum causes the revs to drop gently instead of drastically.

Can a more knowledgeable person (i.e. just about anyone) confirm or correct this explanation?

This was actually what convinced me to do just the lighter pressure plate and not the flywheel. Of course, I just checked the new pressue plate and found it is actually a cast iron plate stuffed into a box for an aluminum plate. So I don't actually HAVE an aluminum pressure plate...grrrrr....after literally thousands of dollars in purchases on eBay, this is the first time I got burned. It will work just fine for my car, but won't be any lighter. At least it was priced well. grrr...

Bill Verburg · Bill Verburg's Garage

Excuse the stupid response from this idiot. But the problem with idle was on the 964/993 where 30#s is saved by using a light flywheel. Not SCs where only a few #s are lost.

Wrecked944 · 08-05-2002, 08:08 PM

"Excuse the stupid response from this idiot."

Excuse me. But that is just plain rude and completely inappropriate. Inexcusable in any context. Period.

Wayne 962 · Wayne 962's Garage

Get up on the wrong side of the bed today Bill?

Everything in this post is true - reducing the rotating mass will make the car rev quicker. Better for racing, probably not too good for the street...

-Wayne

Bill Verburg · Bill Verburg's Garage

Janus, I was refering to myself. Obviously you don't feel that my responses are competent enough to rely on, which I strongly resent. The mods that you are contemplating have been common practice all through the late 70s and 80s and 90s, as a remedy to the very common problems experienced with the rubber center clutches. There have never been any reported idle problems on the SC/Carrera because of it.

Flat6Guy · 08-05-2002, 09:21 PM

Well, I heard or read somewhere the earth was flat. What does that prove? I'm beginning to get tired of these "well I don't really know the answer or understand the problem, but I will confuse the issue with a guess" comments.
Fit the alu pressure plate, you probably won't notice the difference.

Wrecked944 · 08-06-2002, 06:18 AM

Okay, let's resolve this right away. This BBS has been so insanely helpful to me thus far that I won't be the spoiler...

"Janus, I was refering to myself. Obviously you don't feel that my responses are competent enough to rely on, which I strongly resent."

Well, then no worries. I'm genuinely sorry if I took it the wrong way. I'll gladly drop it. As for taking your advice..dude, I ordered the pilot bearing as per your suggestion when you posted the reply. Maybe I've been dismissive of your advice in past threads? If so, then don't take it seriously or personally. I try to make it clear that I make no claims to automotive competence (i.e. my moniker: Wrench Klutz).

"I'm beginning to get tired of these "well I don't really know the answer or understand the problem, but I will confuse the issue with a guess" comments."

Well, certainly true. But in this specific case, Davis911s was reporting an unconfirmed rumor about lightweight pressure plates affecting idle and asking if anyone else had heard about it. I replied saying I had also heard the same rumor, provided details of what I'd heard, and then asked if anyone more knowledgeabe (adding an approriate self-deprecating comment) could provide the real score. Dude, that very scenerio plays itself out on this BBS a zillion times a day and it is enormously helpful to novices trying to sort out conflicting advice and information. It is one of the main reasons I read the stuff on this board.

davis911s · davis911s's Garage

Sorry to bring this post up again but I was a way for a while. I actually recieved a PM from Bill (thanks)

I am sorry I mentioned the unconfirmed rumour but thats all I was doing, trying to find out if it was valid.

Do we need a group hug now???

Shawn

PORSHIN · 08-11-2002, 07:25 PM

Hey Janus,
I have an aluminum pressure plate in my 3.2. I also am running 20/21 cams and stock injection. With the bigger cams, there is more of a chance of idle problems when lightening the flywheel / clutch. I noticed that the engine revs a little quicker but have not experienced any associated problems. If, on the other hand, you were to replace the flywheel AND the pressure plate it might get a little finicky about maintaining a good idle ...especially in a stop-and-go traffic situation. With stock cams, you shouldn't have any problem with an aluminum pressure plate!
Rob

A Quiet Boom · A Quiet Boom's Garage

Well here's my .02c While a lighter flywheel will help the engine rev quicker it can also, depending on the weight of the car, hurt acceleration from a standing start as well as make it more dificult to get the car going normally. The inertia provided by a heavier flywheel helps to get a car moving. In a track situation where standing starts are not important but accelerating the car out of a corner is a lightweight flywheel would be very useful. Given the disadvantages I don't see much point in using a light flywheel on a street car. Back to the question of idle, yes a lighter flywheel can affect idle smoothness if it's significantly lighter than stock but I doubt 4lbs would make much difference. A general rule of thumb is light car/light flywheel, heavy car/ heavy flywheel. Of course the amount of torque on hand and where it peaks also come into play.